You have a good point -- marketing is a skill entirely seperate from skill at 'art' but one which is often required to be better compensated for producing art. That an artist has to market themselves one way or another is no different from the marketing that any other business has to engage in.

Can we frame the question as two different endeavors: creating art, and making a living out of art. Some artists are fortunate enough not to have to worry about the second problem. Those who do need to make a living, either have to find a way to make their art commercially viable, or must devote less time to art (or starve).

Coming back to your intial question, art can very well be created without any expectation of commercial returns -- but those artists who can achieve no commercial returns, and who are not independently wealthy, cannot remain artists indefinitely. Being allowed to devote time to art requires straddling the line between the commercial requirements of making enough to live, and the need of the artist to produce art.